Field of the Invention
The present invention relates to a connection control technique in wireless communication.
Description of the Related Art
In recent years, wireless LAN communication systems, which are represented by IEEE802.11 standard series, are widely used. With a wireless LAN, a base station called an access point (hereinafter, AP) and a station (hereinafter, STA) that exists within an area within which a radio wave of the AP can reach and that is in a wirelessly connected state establish a connection, establish a network, and perform wireless communication. Recently, on more occasions, the IEEE802.11n standard is used with which the communication speed can be raised, among the IEEE802.11 standard series.
IEEE802.11n supports a first mode (hereinafter referred to as “HT20”) in which operation is performed with a conventional 20-MHz frequency bandwidth, and a second mode (hereinafter referred to as “HT40”) in which operation is performed with a 40-MHz frequency bandwidth, which is twice the aforementioned conventional frequency bandwidth, for the purpose of high-speed communication. However, in an environment in which the HT40 is used, there have been cases where a conventional wireless device that does not support IEEE802.11n cannot perform carrier sensing, resulting in a collision between frames. In particular, a 2.4-GHz band is likely to be affected by surrounding BSSes as compared with a 5-GHz band, since wireless channels are overlapped with one another.
For this reason, in IEEE802.11n, OBSS (Overlapping Basic Service Set) Scan is defined for STAs that operate with the 2.4-GHz HT40. The OBSS Scan is a periodic search for surrounding networks performed by a STA operating with the HT40. Specifically, with the OBSS Scan, surrounding wireless networks that do not support the IEEE802.11n standard and surrounding wireless networks that do not allow the HT40 are found. If these wireless networks are found, the STA transmits a report to an AP of the wireless network that the STA has joined. The AP then switches its network from a wireless network that supports the HT40 to a wireless network that supports only the HT20, as necessary. The STA that operates with the 2.4-GHz HT40 needs to execute this OBSS Scan.
On the other hand, methods have emerged for performing communication not only with a simple wireless network configuration using conventional APs and STAs, but also in various modes of wireless LAN network. For example, Tunneled Direct Link Setup (TDLS) has been proposed as a technique for communication between STAs that are connected to an AP, using a direct connection (direct link). IEEE Std 802.11-2012 describes a technique of forming a direct connection between wireless STAs by transmitting and receiving control data for setting TDLS, between wireless LAN terminals via an AP. Since each wireless LAN terminal directly communicates with a partner terminal by forming a direct connection, communication can be performed that is not affected by restriction due to the capability of the AP.
With TDLS, a channel for direct communication between STAs is not fixed to a channel (hereinafter referred to as a “base channel”) of a wireless network configured by the AP and can be switched to another channel (hereinafter referred to as an “off-channel”). As a result, for example, even when the AP operates with a 2.4-GHz band, a STA can directly communicate with the partner STA by using a 5-GHz band channel.
In the present situation, the influence of channel switching for direct communication using TDLS on a connection between an AP and a STA has not been considered. For example, when the operation mode of a connection between an AP and a STA is the 2.4-GHz HT40, the STA is required to periodically execute the OBSS Scan, whereas the problem in switching of the channel in the direct communication in this case has not been examined.
The present invention has been made in view of the aforementioned problem, and provides, in a communication system in which a second connection is established based on a first connection, connection control in which the influence of the second connection on the first connection is considered.